1. Field of the Invention
The present invention pertains to a process for sorting motile from lesser-motile particles, particularly motile and non-motile particles of biological origin, and to apparatus suitable therefor.
2. Background Art
The separation, or “sorting” of motile from lesser-motile and/or non-motile particles has numerous applications, but heretofore has been technologically difficult. For example, in analysis of water supplies, it may be desirable to separate motile bacteria and other microorganisms, including fungi, algae, etc., from those which are non-motile. Identification and enumeration of the various species may thus be facilitated. Examples of motile organisms include flagellated and ciliated bacteria such as C. elegans, and other microorganisms, such as paramecia and motile plankton. Either the motile species enriched or motile species-depleted samples, or both, may be independently analyzed, cultured, etc.
An especially significant application is the sorting of sperm cells. For example, in the case of in vitro fertilization, if the donor's sperm count is low, and especially if contaminated with non-motile sperm, deformed sperm of lesser motility than the desired viable sperm, and other cells and seminal debris, the success rate is raised considerably when the motile sperm are used substantially for fertilization attempts. For example, avoidance of anueploid sperm or DNA fragmented sperm is particularly desirable. In many endeavors, it is desirable to be able to direct the gender of the offspring, for example when the birthing of milk cows is desired. In such cases, it would be advantageous to be able to sort the X- and Y-chromosome containing sperm based on their known motility differences.
Sperm cells from donors with oligozoospermia (low sperm count) have previously been concentrated and to some degree separated from cells and debris having different sizes and/or densities by centrifugation. However, this technique allows incorporation of non-gametes into the enriched sperm sample. These non-gametes, however few there are, release oxygen radicals which are detrimental to continued sperm viability. Moreover, centrifugation is a brute force technique which damages significant numbers of sperm, particularly at the mid-piece and tail regions.
So-called “swim up” techniques are also known, but isolation of the most viable sperm is challenging. S. Smith et al., FERTIL. STERIL. 1995, 63, 591-97. Thus, doctors frequently resort to hand sorting through dead sperm and debris to find sperm which are motile and of distinct morphology, a very time-consuming process.
Applications in biogenetics (biotechnology) also frequently require separation of particles based on their motility. In non-biological application, separation of working microrobots (which are motile) from non-working microrobots is a possible application.